The expedition of Moreau de Maupertuis in 1736

The measurement to prove the oblate form of the globe

To prove the flattening of the Earth and to verify the theoretical calculations by Newton the French Royal Academy of Sciences (Académie Royale de Sciences) sent two expeditions to measure the meridian at the equator and near the poles. One led by La Condamine was sent to Mitad del Mundo at that time in Peru, now in Ecuador and another, led by de Maupertuis, to the River Tornio valley (Swedish Tornedal, Finnish Tornionjokilaakso). A participant in the latter expedition was also Anders Celsius, a famous Swedish physicist, who during his visit in Paris had proposed a measuring expedition to resolve the ongoing debate. The other participants were Clairaut, Camus, Le Monnier and abbot Outhier. A local participant was astronomer Anders Hellant (1717-1789) from Tornio (that time better known by the Swedish name Torneå).

A base line of 14.3 km was accurately measured on the ice-covered River Tornio and with use of that the length of the meridian degree was calculated by means of triangulation. The southernmost point of measurement was the tower of the Tornio Church and the northernmost point was the hill of Kittisvaara 4 km north of the village of Pello. A memorial was erected in 1956 on the hill.

When Maupertuis returned he reported that one meridian degree is in Lapland 57,437.9
toises. (The ancient French unit of length toise was 1.949 meters.) This result when compared to the value of 57,060 toises near Paris proved that the Earth is flattened near the poles just as the theory predicts. Gross errors were later pointed out in the measurements but the conclusions were correct. The king of France rewarded Celsius with an annual pension of 1,000 livres.